For centuries, various natural and unnatural compositions and/or compounds have been added to foods, beverages, and/or comestible (edible) compositions to improve their taste. Although it has long been known that there are only a few basic types of “tastes” (sweet, sour, bitter, salty, and “umami”/savory), the biological and biochemical basis of taste perception was poorly understood, and most taste improving or taste modifying agents have been discovered largely by simple trial and error processes.
For example, one of the five known basic tastes is the “savory” or “umami” flavor of monosodium glutamate (“MSG”), which is now commonly added to many food and beverage compositions to desirably improve their “savory” flavor. MSG is known to produce adverse reactions in some people, but very little progress has been made in identifying artificial substitutes for MSG. It is known that a few naturally occurring materials can increase or enhance the effectiveness of MSG as a savory flavoring agent, so that less MSG is needed for a given flavoring application. For example the naturally occurring nucleotide compounds inosine monophosphate (IMP) or guanosine monophosphate (GMP) are known to have a synergistic and/or multiplier effect on the savory taste of MSG. Nevertheless, IMP and GMP are difficult and expensive to isolate and purify from natural sources, or synthesize, and hence have limited practical application to many commercial needs in food compositions. Less expensive compounds that would provide and/or replace the flavor of MSG itself, or multiply the effectiveness of any MSG that is present so as to replace the need for the addition of IMP or GMP additives could be of very high value, especially if the compounds could be used at extremely low concentrations, so as to minimize costs and any possible health risks.
In recent years substantial progress has been made in biotechnology in general, and in better understanding the underlying biological and biochemical phenomena of taste perception. For example, taste receptor proteins have been recently identified in mammals which are involved in taste perception. Particularly, two different families of G protein coupled receptors believed to be involved in taste perception, T2Rs and T1Rs, have been identified. (See, e.g., Nelson, et al., Cell (2001) 106(3):381-390; Adler, et al., Cell (2000) 100(6):693-702; Chandrashekar, et al., Cell (2000) 100:703-711; Matsunami, et al., Number (2000) 404:601-604; Li, et al., Proc. Natl. Acad. Sci. USA (2002) 99:4962-4966; Montmayeur, et al., Nature Neuroscience (2001) 4(S):492-498: U.S. Pat. No. 6,462,148; and PCT publications WO 02/06254, WO 00/63166 art, WO 02/064631, and WO 03/001876, and U.S. Patent publication US 2003-0232407 A1). The entire disclosures of the articles, patent applications, and issued patents cited immediately above are hereby incorporated herein by reference, for all purposes, including their disclosures of the identities and structures of T2Rs and T1Rs mammalian taste receptor proteins and methods for artificially expressing those receptors in cell lines and using the resulting cell lines for screening compounds as potential “savory” flavoring agents.
Whereas the T2R family includes a family of over 25 genes that are involved in bitter taste perception, the T1Rs only includes three members, T1R1, T1R2 and T1R3. (See Li, et al., Proc. Natl. Acad. Sci. USA (2002) 99:4962-4966.) Recently it was disclosed in WO 02/064631 and/or WO 03/001876 that certain T1R members, when co-expressed in suitable mammalian cell lines, assemble to form functional taste receptors. Particularly it was found that co-expression of T1R1 and T1R3 in a suitable host cell results in a functional T1R1/T1R3 savory (“umami”) taste receptor that responds to savory taste stimuli, including monosodium glutamate. (See Li, et al. (Id.). The references cited above also disclosed assays and/or high throughput screens that measure T1R1/T1R3 or T1R2/T1R3 receptor activity by fluorometric imaging in the presence of the target compounds.
Very recently, certain U.S. and international patent applications have been filed by some of the current Applicants that disclosed the use of certain amide compounds as umami and/or sweet tastants, and/or synergistic enhancers of the “Umami” taste of MSG, and/or the sweet taste of a variety of natural and artificial sweeteners. See, for example, U.S. Provisional Patent Application Ser. No. 60/494,071 filed Aug. 6, 2003, U.S. Provisional Patent Application Ser. No. 60/552,064 filed Mar. 9, 2004, U.S. Utility patent application Ser. No. 10/913,303, filed Aug. 6, 2004 and published as U.S. Patent Publication Serial No. US-2005-0084506-A1 on Apr. 21, 2005; and PCT Patent Application Serial No. PCT/US04/25419 filed Aug. 6, 2004 and published as PCT Publication WO 2005/041684 on May 12, 2005, and PCT Publication WO 2005/015158 published on Feb. 17, 2005. The entire disclosures of the patent applications cited immediately above are hereby incorporated herein by this reference, for all purposes, including their disclosures of the identities and structures of amide compounds that can serve as potential “savory” or sweet flavoring agents or enhancers. Nevertheless, there is a continuing need for new and improved taste enhancing compounds.
We employed the above-described assays and/or high throughput screening methods to identify from a very large number of initial compounds a very few linked heteroaryl “lead” compounds that modulate the activity of T1R1/T1R3 “savory” taste receptors, then embarked on a long, complex and iterative process of investigation, evaluation and revision, and chemical structural optimization, so as to arrive at the various inventions described below.